Pickle Enum flag

It's useful to know something was an enum when it started, and it's necessary to pickle
this when serializing untyped trees.

Author: odersky

compiler/src/dotty/tools/dotc/core/tasty/TastyFormat.scala

@@ -184,6 +184,7 @@ Standard-Section: "ASTs" TopLevelStat*
                   STATIC                              // mapped to static Java member
                   OBJECT                              // an object or its class
                   TRAIT                               // a trait
+                  ENUM                                // a enum class or enum case
                   LOCAL                               // private[this] or protected[this]
                   SYNTHETIC                           // generated by Scala compiler
                   ARTIFACT                            // to be tagged Java Synthetic
@@ -282,21 +283,22 @@ object TastyFormat {
   final val STATIC = 17
   final val OBJECT = 18
   final val TRAIT = 19
-  final val LOCAL = 20
-  final val SYNTHETIC = 21
-  final val ARTIFACT = 22
-  final val MUTABLE = 23
-  final val LABEL = 24
-  final val FIELDaccessor = 25
-  final val CASEaccessor = 26
-  final val COVARIANT = 27
-  final val CONTRAVARIANT = 28
-  final val SCALA2X = 29
-  final val DEFAULTparameterized = 30
-  final val STABLE = 31
-  final val MACRO = 32
-  final val ERASED = 33
-  final val PARAMsetter = 34
+  final val ENUM = 20
+  final val LOCAL = 21
+  final val SYNTHETIC = 22
+  final val ARTIFACT = 23
+  final val MUTABLE = 24
+  final val LABEL = 25
+  final val FIELDaccessor = 26
+  final val CASEaccessor = 27
+  final val COVARIANT = 28
+  final val CONTRAVARIANT = 29
+  final val SCALA2X = 30
+  final val DEFAULTparameterized = 31
+  final val STABLE = 32
+  final val MACRO = 33
+  final val ERASED = 34
+  final val PARAMsetter = 35
 
   // Cat. 2:    tag Nat
 

compiler/src/dotty/tools/dotc/core/tasty/TreePickler.scala

@@ -592,6 +592,7 @@ class TreePickler(pickler: TastyPickler) {
     if (flags is Macro) writeByte(MACRO)
     if (flags is JavaStatic) writeByte(STATIC)
     if (flags is Module) writeByte(OBJECT)
+    if (flags is Enum) writeByte(ENUM)
     if (flags is Local) writeByte(LOCAL)
     if (flags is Synthetic) writeByte(SYNTHETIC)
     if (flags is Artifact) writeByte(ARTIFACT)

compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala

@@ -591,6 +591,7 @@ class TreeUnpickler(reader: TastyReader,
           case STATIC => addFlag(JavaStatic)
           case OBJECT => addFlag(Module)
           case TRAIT => addFlag(Trait)
+          case ENUM => addFlag(Enum)
           case LOCAL => addFlag(Local)
           case SYNTHETIC => addFlag(Synthetic)
           case ARTIFACT => addFlag(Artifact)